In DMOS devices, especially the DMOS devices produced through a semiconductor manufacturing process, the size of SOA (Safe Operating Area) and device long time reliability are two important performance parameters. For a DMOS device, the high electric field near the gate results in high surface electron concentration caused by impact ionization. This phenomenon affects SOA size and device long time reliability.
Hence how to effectively reduce and control the amount of electric field near the gate directly affects SOA size and device long time reliability of the DMOS device.